Curtis argues for small scale mini monocultures for productive urban farming, do you buy the argument? I call these intensive farming and market-driven monocultures because they’re all about consumerism and the ease of harvest and driving produce to market efficiently, yet at potentially some expense to environmental sustainability and diversity depending on the inputs and outputs.

An expense that appears inevitable in modern society, yet how do we quantify that? How many urban farming plots like Curtis’ could a local ecosystem tolerate before diversity suffered or does it actually increase diversity? Where is the balance? Are these it? Can these systems be made even more environmentally friendly while still maintaining the productivity? He certainly sounds like he’s tried.

If you look at Zaytuna Farm you also see these mini monocultures with diverse row cropping. Are these kinds of systems the best we can come up with for intensive farming?

Same applies to Richard Perkins, planting six varieties meeting more market demand for lettuce mixes.

It makes me wonder what a diversity audit in an urban farming setting might look like.

Are these farmers making a Zone 1 argument and that makes it acceptable in an urban farming environment because it’s close to where the produce will be consumed and can be tended to with little resources like Curtis’ bicycle?

Still, a part of me likens these kinds prosumer arguments to that of Lyle Landly from The Simpsons, with Lisa and Marge questioning the motive.

Is the real answer Barts; “Sorry environmentalists, the mob has spoken?”

When the microbes aren’t doing the work because they’re not being watered, housed and fed well, some farmers do that work for them.

In the video from India they explain how they use dried topsoil and subsoil for fertigating their crops via foliar spray. This has multiple effects, the first is providing soluble and insoluble nutrients to the plant surfaces for plants, microbes and sunlight to break them down, and second is adding to existing topsoil where more active microbes may utilise them.

However care should be taken as many clays from subsoils are known to have antibiotic effects, even on superbugs, and the application of foliar sprays with these clays has been shown to eliminate some plant pests and diseases. Many subsoils also have low pH that make kill some microbes.

So on one hand applying subsoil may be supplying nutrients and could increase productivity, and this appears to be the case in India. On the other and depending on the soil it could initially be killing the plant and soil microbes that produce them. This can potentially break the natural cycle and make this a system that requires continuous human intervention.

In the video they recommend 3:1 dried topsoil to dried subsoil in their foliar spray, with that increasing in subsoil content to 1:3 for disease eradication.

Every 10 days or even weekly…

They are effectively mining the soil to liquid feed the plants for continuous cropping.

Whether this is sustainable or even regenerative is a good question.

Does this practice build soil over time? Could it? Is that building as much as they excavate and does it compensate for the energy used to distribute those nutrients? They do mention increased plant nutrients, but I’m not sure if they also tested the soils.

On one hand the drying of soils is effectively hunting and killing microbes and their mucilages for their nutrients, on the other you get increased productivity. It’s like robbing Peter to pay Paul, which is the best investment? The same applies to killing off plant predators with foliar spraying, effectively feeding the plants with dead microbes and dead soil.

But perhaps this produces more plant exudates that produce more symbiotic root microbes to kickstart nutrient cycling above the level in the root zone needed to build soil rather than consume it?

If done in combination with diverse cover cropping and chop and drop to provide a cover and food for the soil I can see it being a useful tool to help get back to letting nature do the work, instead of the farmer.I think of this in the same way as I think of tillage. Initial minimal tillage can kickstart a system faster towards a regenerative approach by decompacting soils and releasing nutrients for plants to establish and grow and photosynthesise thereby feeding more microbes that build soil and reduce soil density.

Adrianna MarchandIn a lot of ways it also reminds me of the Soilkee Renovator. Here they only disturb strips of the topsoil and bring organic matter to the soil surface to dry and oxidise it, thereby killing microbes and releasing their nutrients and mucilages to feed the soil and surviving plants. And from results I’ve seen it reduces initial organic matter and trades it for soluble nutrients that feeds the microbes that produces plant available nitrogen and other nutrients. Thereby generating a burst of fresh growth and photosynthesis. It also appears to recover that lost organic matter over about a year. So not something you’d want to do regularly but it certainly could help kickstart nutrient cycling, especially where they trialled as they had existing high carbon levels. The effect is likely similar to that seen when soils dry and rewet and produce CO2-bursts.There’s hope these farmers will eventually use any additional fertility to transition to a more regenerative farming approach. That this could be a tool in the regenerative farmers toolbox when they have little initial nutrient cycling to help get started, but it’s also open to abuse when misunderstood.
It’s important to keep in mind too that tilling kills off fungi and earthworms, and so using any technique that disturbs soil should be minimised.In situations when access to organic matter is limited I can see these approaches helping get an initial crop in the ground to then be regeneratively managed. On the other hand where there is plenty of organic matter and soil moisture a no dig approach may be more appropriate.

The material was found to harbor a bacterial community of 2.38 × 10-8CFU/g dw dominated by Gram-positives with minor instances of Actinobacteria and Gammaproteobacteria. ARISA showed a coherence of bacterial assemblages in different preparation lots of the same year in spite of geographic origin. Enzymatic

activities showed elevated values of β-glucosidase, alkaline phosphatase, chitinase, and esterase. The preparation had no quorum sensing-detectable signal, and no rhizobial nod gene-inducing properties, but displayed a strong auxin-like effect on plants. Enzymatic analyses indicated a bioactive potential in the fertility and nutrient cycling contexts. The IAA activity and microbial degradation products qualify for a possible activity as soil biostimulants.

Of the bacterial species, two dominated 90% of the culture. Half was Bacillus megaterium a plant growth promoting rhizobacteria (PGPR) known to produce Cytokinin. While the other half was Bacillus safensis another PGPR known to produce Auxins.

The above quote was left as a reply to a comment I’d left on a big ag research and education industry video talking about cover crops ages ago. It still irks me that these people are so ignorant.

Today I read the following study on plant species diversity’s impact on soil ecosystems, albeit in a conservation and restoration context that ends up restoring degraded agricultural lands these people create:

Restoring and managing for more diverse plant communities can improve recovery of belowground biology and functioning in predictable ways. Specifically, we found greater accumulation of roots, more predictable recovery of soil microorganisms (bacteria and fungal biomass), more rapid improvement in soil structure (less compaction), and less nitrogen available for loss from the system in prairie restored and managed for high plant diversity (>30 species) relative to the low diversity (<10 species) grassland plantings. Thus, the hypothesis that biodiversity promotes ecosystem functioning is relevant to large-scale conservation and restoration practices on the landscape.

Whenever designing a drip system the first thing you need to decide on is the drippers. Whether it’s do it yourself or commercial I’d first find out the drip tube or dripping system technical information for pressure rating, drip spacing, and flow rate. Pressure is especially important for gravity-fed systems.

To begin with you need to decide if you want Pressure Compensation (PC) drippers to account for elevation change. For every 1 meter of elevation change there is a 9.8 kPa pressure change with it. That 1 meter is 10% of the 100 kPa (1 bar) minimum recommended for most commercial drip tubes. A 10 meter change in elevation may see the highest drippers simply not drip and others just end up blocking because of the low pressure. Assuming sufficient flow rate, drip lines higher in the landscape will see less pressure the higher they are relative to the bottom drip lines where gravity wants the water to naturally run to. Without a high enough flow rate, there may not be enough water to pressurise the top drippers. The length of piping an drip tubes and whether they’re made into a loop also matters as pipes have friction losses and pressure equalisation to take into account.

Most commercial drip tubes should work fine with about 1 bar (14.7 psi, 100 kPa, 10.2 meter head) if they actually get 1 bar. For example this PC drip tube only needs 50 kPa (0.5 Bar) for pressure compensation but recommends 100 kPa (1 bar) minimum. In general, the higher the pressure, the less likely the drippers are to block, but it depends on the dripper and water. Some drippers are designed to oscillate to clear blockages but need pressure to do so, and pressure is often short in supply in gravity-fed systems not designed well.

For extremely low pressure systems or low drip flow rates that resist blockages, you’re better off looking at wick siphon irrigation, which I will cover that at a later date.

Sizing your piping and connectors for flow rate based upon how many drippers you use and their flow rate matters a lot in any irrigation system, but especially gravity-fed where the pressure is generally lower. You must also account for the pipe & connector friction losses mentioned in gravity-fed systems in order to deliver the pressure needed at the dripper.
You can find pressure drop calculators to help you there. Remember that the longer the pipe, the more pressure drop. So if you have to run a long pipe to your garden, it’s always best to go large for gravity-fed. That includes the internal size of the connectors and any fittings. As one simple flow restriction upstream could ruin your plants day.

Now that you know the size of pipe you need to supply the water to the drippers, you have to get that water from somewhere, and here I’m covering a gravity-fed pond system.

A submerged pipe and pond inlet that is floated just below the surface and moved with the water level but prevented from landing on the bottom is one way to then feed a sediment filter without sucking in lots of debris. This can then be fed to a filtration system such that your drippers don’t block. Another way is to use a pond siphon where the piping runs higher than the water level in order to help prevent debris entering.

Many people think using a mesh filter on the inlet is a good idea, however they can be problematic if not well designed. If you do use a plain mesh inlet filter, I’d make the mesh area large and make the mesh the lowest point of the inlet so that when you weren’t watering, anything large sucked against the mesh would drop away. A cone mesh filter with the peak pointing down for example. Cones have larger surface areas!

I can’t help you with pond filter sediment experience, however there are a lot of commercial and homemade designs out there. Ideally you add a pressure gauge before and after whatever filter you use. That way you’ll know if it’s performing as expected, or the pipe leading to it is blocked(likely the inlet). Add a valve before the filter too for maintenance. Personally I’d probably want a large high flow biological filter I never had to clean. I’d make mine a submersible cylinder mesh with multiple cylindrical layers of filter medium, with the inlet in the middle of it. Let the microbes live on the filter medium and clean the water naturally I say. Might be a bit of a bastard getting it into the middle of a large pond though. 🙂

However if that level of filtration or water treatment isn’t enough there are large commercial systems by Puricare that treat water by oxidation to help prevent irrigation blockage. It uses an ozone generator, a UV light and hydrogen peroxide to produce hydroxyl radicals. In India rather than filter or treat they use simple non-pressure compensating button drippers because of high hardness bore (calcium and magnesium) water blocking most drippers, they can be unplugged cleared and plugged back in. There’s also evidence Magnetically treated water can help reduce the build up of these divalent elements in hard water.

Once you have your water, filter, treatment, piping and drippers all worked out, you may want to automatically control their operation. Electronic soil moisture or timer controllers are one option, there are lots of those around and it’s what most people use. Tropf Blumat is a passive system for home gardens and doesn’t need electronics, but I don’t believe they have a commercial version. Evapotranspiration as used in Aqualone and Measured Irrigation are other options.

Others I know of include siphon watering timers where water is dripped into a siphon container and once the water level reaches the siphon outlet it over flows, siphoning water to plants, empties, and then starts the drip timer process again.

Personally I like evapotranspiration controllers like Aqualone. Before I knew about theirs I made one of my own design that’s more redundant, but I’m trying to simplify it to come up with a good design that doesn’t require magnets, or like mine; pressure valves. Ideally I want one that anyone could make that will hold mains (500 kPa) pressure and be easily made by anyone anywhere.

Ideally we want a diverse range of mulch and C:N ratios such that we get a diverse range of biology. I’d wondered what that range might be so did some digging, or should that be mulching? Here’s one paper.

Effects of carbon concentration and carbon to nitrogen (C:N) ratio on six biocontrol fungal strains are reported in this paper. All fungal strains had extensive growth on the media supplemented with 6–12 g l−1 carbon and C:N ratios from 10:1 to 80:1, and differed in nutrient requirements for sporulation. Except for the two strains of Paecilomyces lilacinus, all selected fungi attained the highest spore yields at a C:N ratio of 160:1

Seems to confirm that for fungi to reproduce and sporulate, that they need a constant supply of carbon. Note that the study only went to 160:1, and more carbon could be more desirable.

If you look at this chart I made, the curve is steepest at the peak between about 18:1 and 50:1, this range seems likely to be the sweet spot for fungi and for soil carbon priming, however to reproduce fungi, material with a higher C:N is also desirable.

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